Last week I was chatting with some mathematicians and I mentioned the blog post that I wrote last year on the distribution of Pythagorean triples. In my previous article, I showed that there is an algorithm that uses matrix multiplication to generate every primitive Pythagorean triple by starting with the
Today is my 600th blog post for The DO Loop. I have written about many topics that are related to statistical programming, math, statistics, simulation, numerical analysis, matrix computations, and more. The right sidebar of my blog contains a tag cloud that links to many topics. What topics do you,
A common question from statistical programmers is how to compute the rank of a matrix in SAS. Recall that the rank of a matrix is defined as the number of linearly independent columns in the matrix. (Equivalently, the number of linearly independent rows.) This article describes how to compute the
The 2015 SAS Global Forum is in Dallas, TX, and I'll be there. There are many talks to see and people to meet, so thank goodness for the agenda builder, which enables you to create a schedule in advance. I always enjoy talking with SAS customers about statistics, simulations, matrix
The Monty Hall Problem is one of the most famous problems in elementary probability. It is famous because the correct solution is counter-intuitive and because it caused an uproar when it appeared in the "Ask Marilyn" column in Parade magazine in 1990. Discussing the problem has been known to create
There has been a spate of recent high-profile airline crashes (Malaysia Airlines, TransAsia Airways, Germanwings,...) so I was surprised when I saw a time series plot of the number of airline crashes by year, which indicates that the annual number of airline crashes has been decreasing since 1993. The data
There's "big," and then there is "factorial big." If you have k items, the number of permutations is "k factorial," which is written as k!. The factorial function gets big fast. For example, the value of k! for several values of k is shown in the following table. You can
The title of this article makes no sense. How can the number of elements (in fact, the number of anything!) not be a whole number? In fact, it can't. However, the title refers to the fact that you might compute a quantity that ought to be an integer, but is
Imagine that you have one million rows of numerical data and you want to determine if a particular "target" value occurs. How might you find where the value occurs? For univariate data, this is an easy problem. In the SAS DATA step you can use a WHERE clause or a
This article show how to run a SAS program in batch mode and send parameters into the program by specifying the parameters when you run SAS from a command line interface. This technique has many uses, one of which is to split a long-running SAS computation into a series of
